GNU Radio 3.7.0 C++ API
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00001 /* -*- c++ -*- */ 00002 /* 00003 * Copyright 2009,2010,2012 Free Software Foundation, Inc. 00004 * 00005 * This file is part of GNU Radio 00006 * 00007 * GNU Radio is free software; you can redistribute it and/or modify 00008 * it under the terms of the GNU General Public License as published by 00009 * the Free Software Foundation; either version 3, or (at your option) 00010 * any later version. 00011 * 00012 * GNU Radio is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00015 * GNU General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU General Public License 00018 * along with GNU Radio; see the file COPYING. If not, write to 00019 * the Free Software Foundation, Inc., 51 Franklin Street, 00020 * Boston, MA 02110-1301, USA. 00021 */ 00022 00023 00024 #ifndef INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H 00025 #define INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H 00026 00027 #include <gnuradio/filter/api.h> 00028 #include <gnuradio/block.h> 00029 00030 namespace gr { 00031 namespace filter { 00032 00033 /*! 00034 * \brief Polyphase filterbank channelizer with 00035 * gr_complex input, gr_complex output and float taps 00036 * \ingroup channelizers_blk 00037 * 00038 * \details 00039 * This block takes in complex inputs and channelizes it to <EM>M</EM> 00040 * channels of equal bandwidth. Each of the resulting channels is 00041 * decimated to the new rate that is the input sampling rate 00042 * <EM>fs</EM> divided by the number of channels, <EM>M</EM>. 00043 * 00044 * The PFB channelizer code takes the taps generated above and builds 00045 * a set of filters. The set contains <EM>M</EM> number of filters 00046 * and each filter contains ceil(taps.size()/decim) number of taps. 00047 * Each tap from the filter prototype is sequentially inserted into 00048 * the next filter. When all of the input taps are used, the remaining 00049 * filters in the filterbank are filled out with 0's to make sure each 00050 * filter has the same number of taps. 00051 * 00052 * Each filter operates using the gr::blocks::fir_filter_XXX 00053 * classs of GNU Radio, which takes the input stream at <EM>i</EM> 00054 * and performs the inner product calculation to <EM>i+(n-1)</EM> 00055 * where <EM>n</EM> is the number of filter taps. To efficiently 00056 * handle this in the GNU Radio structure, each filter input must 00057 * come from its own input stream. So the channelizer must be 00058 * provided with <EM>M</EM> streams where the input stream has 00059 * been deinterleaved. This is most easily done using the 00060 * gr::blocks::stream_to_streams block. 00061 * 00062 * The output is then produced as a vector, where index <EM>i</EM> 00063 * in the vector is the next sample from the <EM>i</EM>th 00064 * channel. This is most easily handled by sending the output to a 00065 * gr::blocks::vector_to_streams block to handle the conversion 00066 * and passing <EM>M</EM> streams out. 00067 * 00068 * The input and output formatting is done using a hier_block2 called 00069 * pfb_channelizer_ccf. This can take in a single stream and outputs 00070 * <EM>M</EM> streams based on the behavior described above. 00071 * 00072 * The filter's taps should be based on the input sampling rate. 00073 * 00074 * For example, using the GNU Radio's firdes utility to building 00075 * filters, we build a low-pass filter with a sampling rate of 00076 * <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition 00077 * bandwidth of <EM>TB</EM>. We can also specify the out-of-band 00078 * attenuation to use, <EM>ATT</EM>, and the filter window 00079 * function (a Blackman-harris window in this case). The first input 00080 * is the gain of the filter, which we specify here as unity. 00081 * 00082 * <B><EM>self._taps = filter.firdes.low_pass_2(1, fs, BW, TB, 00083 * attenuation_dB=ATT, window=filter.firdes.WIN_BLACKMAN_hARRIS)</EM></B> 00084 * 00085 * The filter output can also be overs ampled. The over sampling rate 00086 * is the ratio of the the actual output sampling rate to the normal 00087 * output sampling rate. It must be rationally related to the number 00088 * of channels as N/i for i in [1,N], which gives an outputsample rate 00089 * of [fs/N, fs] where fs is the input sample rate and N is the number 00090 * of channels. 00091 * 00092 * For example, for 6 channels with fs = 6000 Hz, the normal rate is 00093 * 6000/6 = 1000 Hz. Allowable oversampling rates are 6/6, 6/5, 6/4, 00094 * 6/3, 6/2, and 6/1 where the output sample rate of a 6/1 oversample 00095 * ratio is 6000 Hz, or 6 times the normal 1000 Hz. A rate of 6/5 = 1.2, 00096 * so the output rate would be 1200 Hz. 00097 * 00098 * The theory behind this block can be found in Chapter 6 of 00099 * the following book. 00100 * 00101 * <B><EM>f. harris, "Multirate Signal Processing for Communication 00102 * Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.</EM></B> 00103 * 00104 */ 00105 00106 class FILTER_API pfb_channelizer_ccf : virtual public block 00107 { 00108 public: 00109 // gr::filter::pfb_channelizer_ccf::sptr 00110 typedef boost::shared_ptr<pfb_channelizer_ccf> sptr; 00111 00112 /*! 00113 * Build the polyphase filterbank decimator. 00114 * \param numchans (unsigned integer) Specifies the number of 00115 * channels <EM>M</EM> 00116 * \param taps (vector/list of floats) The prototype filter to 00117 * populate the filterbank. 00118 * \param oversample_rate (float) The over sampling rate is the 00119 * ratio of the the actual output 00120 * sampling rate to the normal 00121 * output sampling rate. It must 00122 * be rationally related to the 00123 * number of channels as N/i for 00124 * i in [1,N], which gives an 00125 * outputsample rate of [fs/N, 00126 * fs] where fs is the input 00127 * sample rate and N is the 00128 * number of channels. 00129 * 00130 * For example, for 6 channels 00131 * with fs = 6000 Hz, the normal 00132 * rateis 6000/6 = 1000 00133 * Hz. Allowable oversampling 00134 * rates are 6/6, 6/5, 6/4, 6/3, 00135 * 6/2, and 6/1 where the output 00136 * sample rate of a 6/1 00137 * oversample ratio is 6000 Hz, 00138 * or 6 times the normal 1000 Hz. 00139 */ 00140 static sptr make(unsigned int numchans, 00141 const std::vector<float> &taps, 00142 float oversample_rate); 00143 00144 /*! 00145 * Resets the filterbank's filter taps with the new prototype filter 00146 * \param taps (vector/list of floats) The prototype filter to populate the filterbank. 00147 */ 00148 virtual void set_taps(const std::vector<float> &taps) = 0; 00149 00150 /*! 00151 * Print all of the filterbank taps to screen. 00152 */ 00153 virtual void print_taps() = 0; 00154 00155 /*! 00156 * Return a vector<vector<>> of the filterbank taps 00157 */ 00158 virtual std::vector<std::vector<float> > taps() const = 0; 00159 00160 /*! 00161 * Set the channel map. Channels are numbers as: 00162 * 00163 * N/2+1 | ... | N-1 | 0 | 1 | 2 | ... | N/2 00164 * <------------------- 0 --------------------> 00165 * freq 00166 * 00167 * So output stream 0 comes from channel 0, etc. Setting a new 00168 * channel map allows the user to specify which channel in frequency 00169 * he/she wants to got to which output stream. 00170 * 00171 * The map should have the same number of elements as the number 00172 * of output connections from the block. The minimum value of 00173 * the map is 0 (for the 0th channel) and the maximum number is 00174 * N-1 where N is the number of channels. 00175 * 00176 * We specify M as the number of output connections made where M 00177 * <= N, so only M out of N channels are driven to an output 00178 * stream. The number of items in the channel map should be at 00179 * least M long. If there are more channels specified, any value 00180 * in the map over M-1 will be ignored. If the size of the map 00181 * is less than M the behavior is unknown (we don't wish to 00182 * check every entry into the work function). 00183 * 00184 * This means that if the channelizer is splitting the signal up 00185 * into N channels but only M channels are specified in the map 00186 * (where M <= N), then M output streams must be connected and 00187 * the map and the channel numbers used must be less than 00188 * N-1. Output channel number can be reused, too. By default, 00189 * the map is [0...M-1] with M = N. 00190 */ 00191 virtual void set_channel_map(const std::vector<int> &map) = 0; 00192 00193 /*! 00194 * Gets the current channel map. 00195 */ 00196 virtual std::vector<int> channel_map() const = 0; 00197 }; 00198 00199 } /* namespace filter */ 00200 } /* namespace gr */ 00201 00202 #endif /* INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H */